Retarded type switch control arrangement for a drier

ABSTRACT

A control circuit for a drier having a heater, blower and a motor for a sensor mounted within the drier housing for determining the water content of the material therein. A desired dryness of the material is set by a manually settable control switch and a spring driven switching mechanism actuated by the control switch actuates a plurality of switches each individually controlling the heater, blower and motor. A control circuit comprises the wetness of the material within the drier with the setting of the control switch whereby the spring driven switching mechanism is unlocked to return the control switch to &#39;&#39;&#39;&#39;zero&#39;&#39;&#39;&#39; so as to prevent further drying of the material.

United States Patent [191 Apel RETARDED TYPE SWITCH CONTROL ARRANGEMENT FOR A DRIER [76] Inventor: Konstantin Apel, Lehrenweg 8, D-

7758 Meersburg, Germany [22] Filed: May 14, 1971 [21] Appl. No.: 143,519

[30] Foreign Application Priority Data May 14, 1970 Switzerland ..7l93/70 [52] US. Cl. ..200/33 R, 307/l4l.4 [5 l Int. Cl. ..H0lh 43/00 [58] Field of Search ..200/33 R, 35 R, 38 R,

200/38 B, 38 C; 34/37, 63, 68; 68/12 R, 12 F; 307/1414; 219/492, 493

3,163,029 12/]964 Jacobs ..34/37X 14 1 Apr. 10, 1973 3,242,584 3/1966 Jacobs .34/68 X 3,402,576 9/l968 Krupsky ..68/l2 R X 2,953,653 9/1960 Demon ..200/33 R 2,868,287 l/l959 Estey ..200/35 R X Primary Examiner-J. R. Scott Attorney-Watson, Cole, Grindle & Watson [5 7 ABSTRACT A control circuit for a drier having a heater, blower and a motor for a sensor mounted within the drier housing for determining the water content of the material therein. A desired dryness of the material is set by a manually settable control switch and a spring driven switching mechanism actuated by the control switch actuates a plurality of switches each individually controlling the heater, blower and motor. A control circuit comprises the wetness of the material within the drier with the setting of the control switch whereby the spring driven switching mechanism is unlocked to return the control switch to zero so as to prevent further drying of the material.

4 Claims, 4 Drawing Figures PATENTED 1 01975 3 7 27. 014

sum 1 UF 2 INYENTURI z; a W

ATTOIiNEY'.

RETARDED TYPE SWITCH CONTROL ARRANGEMENT FOR A DRIER The invention relates to a control arrangement for a drier with an apparatus for circulation of heated air and with electrodes to scan the material that is to be dried to determine the amount of water on humidity in the material.

Customarily, driers are controlled either by mechanical time switches or by electronic installations. The mechanical time switches are started at the beginning of the operating cycle and turn off the drier again after a predetermined time. This type of control is disadvantageous in that, because of the varying starting wetness of the material to be dried, its degree of drying cannot be predetermined unequivocally. The dried material then must again be returned to an additional operating process to the desired degree of drying after the initial drying process has been completed.

Electronic control arrangements attain their control value by sensing electrodes which scan the material which is to be dried. In this case the control input of the electronic device can be changed directly by way of sensing electrodes and the electric resistance of the material to be dried or else the charge of a capacitor is transmitted via the electric resistance of the goods to be dried and via sensing electrodes to the input of the electronic system. The control electronics on their part then, upon reaching a certain previously adjusted threshold, will turn the drier off. Electronic control arrangements, however, have the disadvantage that their control input must have an extremely high impedance. In order to be able to measure even very low degrees of dampness, the control arrangement must have an input resistance in the order of magnitude of about 500 MOhm. An electronic system with such a high impedance must be structured very carefully and, in operation, it is particularly susceptible to breakdowns as a result of the fact that the humid atmosphere of the surroundings leads to unintended changes in the input resistance. Besides, an expensive power relay must be used to switch the drier in addition to the expensive electronic system.

It is the object of the invention to create a control arrangement which will avoid the above mentioned disadvantages of the heretofore customary installations, and which can be set up relatively simply and economically and which will operate reliably. A residual dampness of the material to be dried, which can be adjusted in advance, is achieved reliably. In the case of the control arrangement, it is possible to avoid use of expensive power relays. According to the invention, a spring driven time switch, provided with an unwinding lock, provides the power connection of the drier, is wound by hand, and the unwinding lock is released via an elec tronic arrangement known per se after reaching a preset degree of drying. The supply of power to the individual components of the drierpartially in succession-is interrupted prior to the unwinding of the time switch.

The control arrangement according to the invention and compared to the hitherto customary arrangement has the advantage that an electronic system with a relatively low impedance can be used. Since the electronic system signals a definite value of residual moisture to the mechanical time switch, it will be possible to achieve very exactly the residual dampness desired after completion of the process. In switching off the power for the drier by the mechanical system, an expensive power relay is unnecessary. Furthermore, the mechanical system can produce an acoustical signal directly which signals the end of the drying process.

According to one development of the invention, the individual components of the drier can be switched on or off by means of cam operated switches.

According to another development of the invention, the switch, attached on at least one cam disk or roller, can be operated by cam followers or by corresponding slits.

A further practical development of the invention provides that the mechanical transmission of power between the spring driven cam disk or roller and the unwinding inhibitor is interrupted between the two positions zero and stop of a knob serving for the manual winding of the time switch.

According to a further development of the invention, the unwinding lock can be released by means ofa magnet.

According to another development of the invention, the unwinding lock with a nonenergized winding of the magnet is in a released position and with the winding of the magnet energized it can be put into the locking position.

According to still another development of the invention, a mechanical bell can be operated by the time switch to signal the end of the operation of the drier.

According to a further development of the invention, the time for turning off the heat can be selected freely, depending on the time of switching off the entire drying operation.

Another development of the invention provides that the magnet will obtain a low voltage from the electronic installation during its operation.

According to a practical development of the invention, the knob is developed as an indicator knob.

A further development of the invention provides that a scale showing values of moisture of the material to be dried is calibrated and surrounds the knob.

According to a further development of the invention, the unwinding lock acts upon the anchor of the inhibiting mechanism.

According to another development of the invention, the unwinding lock acts upon the balance or on its lever disk.

The invention will be explained on the basis of an embodiment given by way of example and with the aid of drawings. In the drawings:

FIG. 1 shows the control arrangement in perspective,

FIG. 2 shows the operating knob of the mechanical time switch with the pertinent scale,

FIG. 3 shows a current circuit in accordance with the invention,

FIG. 4 shows a closing diagram of the individual contacts used in the control arrangement.

Some material that is to be dried is placed in a drum 4 (FIG. 1). For this purpose the drum is rotated by a driving motor 29 and, at the same time, air is conducted to the inside of the drum by means of a blower 27, which is preheated with the aid of the heating system 28. Sensing electrodes 5 are attached in drum 4 for the purpose of scanning the electric transition resistance of the material that is to be dried. The sensing electrodes are connected directly with the input of an electronic installation 1. Instead of the direct measurement of the transition resistance, a capacitor discharge type system, known per se, can be used.

The electronic arrangement 1 measures the relatively high residual dampness of the material to be dried and, upon sensing this residual dampness, operates a mechanical system. The relatively high value of the residual dampness, for example 20 percent, will permit the construction of the electronic arrangement with relatively low impedance. While hitherto customary electronic control arrangements had to have an input resistance in the order of magnitude of about 500 MOhm, the control arrangement of the object of the application operate with an input resistance in the order of 4 to 5 MOhm.

The basic function of the object of the application will be first explained on the basis of FIG. 3. In order to be able to start the drier, by way of example, a cam disk 16 is turned, which is provided via a shaft with a knob for manual operation. In the case of this operation, two switches 30 and 30 are switched on, which serve as powerswitches. With the power switches on, the electronic control arrangement 1 is energized with a supply voltage and simultaneously the heaters in the drier are switched on or prepared for switchingon and the driving motor 29 for driving drum 4 (FIG. 1) as well as blower 27 are actuated. Cam disk 16 is developed in such a way that it switches on the programming switch 33 simultaneously, which connects the heating system 28 to a mains 3. The electronic system 1, heating system 28, motor 29 and blower 27 now are connected to mains 3.

Cam disk l6, in place of which naturally several cam disks or cam rollers can be used, is connected with a gear 24 which'is braked by armature 7 of a relay 6 which responds to the tractive force of a spring ,8.

In the case of the previously mentioned turning of cam disk 16, a spring is simultaneously wound, which will return the cam disk and with it knob 10 to its starting position. Electrodes 5 are located at the input of electronic system 1 for scanning the goods that are to be dried. The electronic control arrangement 1 is set to a certain value of residual dampness, for example, to percent. As soon as this residual dampness is reached, the winding of relay 6 is energized by the electronic control arrangement 1, the armature 7 of the relay attracts and gear 24, which is turned by cam disk 16, can run down freely.

From the switch closing diagram shown in FIG. 4, it is clear'how the contacts shown in FIG. 3 close or open. Let it beassumed that position 0 of the switch closing diagram is identical to the beginning of the drying process. The closing diagram this case will be run through in the direction of an arrow 14. Switches 30 and 30' acting as the main contacts of the mains are closed during the entiredrying process from position 0 to position 0. At the beginning of the drying process, switch 33 also is closed, which feeds current to the heating system 28 and remains closed until the actual drying process is completed (point dry in the switch closing diagram). After turning heating system 28 off, the blower is operated for still a certain period of time in order that the drying space can cool off again. A certain time prior to switching off the entire drier, a'switch 31 will connect a signal lamp 26 with the mains 3.In this way the end of the drying time will be signaled. Instead of lamp 26, an alarm 37 could just as well be used, which then would be switched on via a switch 32.

Instead of a driving motor 29 for drum 4, and a blower 27, the blower naturally can also be mounted on the motor. Nothing will change per se as a result in regard to the control arrangement. The mechanical system of the time switch will be explained on the basis of FIG. 1 by way ofan embodiment given as an example. When switching on a drier, an operating knob 10 is turned in the direction of arrow 19. A spiral spring 12 or a volute buffer spring is thereby wound, and has been attached at one end to the housing and with its other end to a shaft 11 connected with knob 10.

On shaft 11, moreover, a camdisk 16 has been rotatably mounted. Naturally, instead of cam disk 16, a cam roll can be used just as well as several cam disks one beside the other. Cam disk 16, used in the embodiment given by way of example, is scanned by switches 31, 32, 33, 30, 30'. Instead of earns, the disk naturally may also have slits. Furthermore, a gear 23 is attached to shaft 11 which has gear teeth 25. Upon turning the knob in the direction described, gear23 also will turn in the direction of arrow 20. Teeth 25 of this gear mesh with the teeth of an inhibiting gear 24. The inhibiting gear 24 operates together with an anchor 34, which can be controlled by a balance or a lever disk 36.

The conveying teeth of inhibiting gear 24 have been mounted to a separate. disk, which is not capable of driving the inhibiting gear on the basis of a coupling arrangement between it and the inhibiting gear as soon as the teeth are moved in the direction of arrow 21. In the opposite direction however, a mechanical connection will be established between the inhibiting gear 24 and its conveying teeth. As soon as knob 10 is released after turning in the direction of arrow 19, spring 12 will try to return the knob and with it cam disk 16 and gear 23. However, this can take place only slowly, since now inhibiting gear 24 becomes effective in connection with armature 34 and lever disk 36. An armature 7 of a magnet 6 carries a peg 35. Armature 7 is mounted rotatably around an axle 9 and is under pressure of a tension spring 8. In case the winding of magnet 6 is not energized, armature 7 therefore will not prevent armature 34 of the inhibitor via peg 35 in the manner shown in FIG. 1 from moving freely. Thus the entire inhibitor is also blocked and cam disk 16 cannot return to its starting position.

The electronic system 1 will scan the material that is to be dried via sensing electrodes 5 until the preset and relatively high value of the residual dampness is reached. From this time on magnet 6 will be energized. Armature 7 of magnet 6 is attracted by the latter and thus releases the armature of the inhibitor. Cam disk 16 and thus also knob 10 can return to their starting position until cam disk 16 strikes with its projection 22 against a stop 13 which is fixed in the housing.

Shortly prior to cam disk 16 reaching its starting position again, a bell 37 is operated by way of a mechanical system shown by way of example only in FIG. 1.

In the case of another type of application, it could just as well be armature 34 of the inhibitor that is released, armature 7 of the magnet being in its rest switches 30 and 30' as well as switch 33 for the heating system are switched on, as described in detail above. Depending on how far knob is turned, the drier will dry the material more or less intensively. The knob,

therefore, may be set to 6 percent residual moisture. As soon as the predetermined residual moisture of for example percent is reached in the electronic system, knob 10 begins again to move counter to arrow 19. As soon as it reaches 0, it snaps back to the STOP" position. This will be accomplished due to teeth (FIG. 1) being interrupted in this area; it therefore will be disengaged from the conveying teeth of the inhibiting gear 24 at the 0 position.

Naturally, other values of residual moisture can be used on the scale in FIG. 2. Likewise the percentage values could also be replaced by words, such as for example DAMP, HALF DRY and DRY."

What is claimed is:

1. Apparatus for controlling a drier, comprising:

a heater, blower, and motor for providing rotative movement;

a rotatable drier housing;

means mounted within said housing for determining the water content of the material within said housmg;

switching means for controlling the operation of at least said motor, heater and blower;

a manually settable control switch for setting the desired dryness of said material;

a spring driven switching mechanism actuated by settable control switch for controlling said switching means;

a control circuit for comparing the wetness of said material with said value of preset dryness; and

means for locking said spring driven switching mechanism whereby said spring driven switching mechanism is unlocked with said control means indicating that said material has reached said desired degree of dryness, said means for locking is inoperative prior to actuation by said control means.

2. Apparatus as in claim 1 further comprising a rotatable shaft interconnecting said manually settable control switch and said spring driven switching mechanism, said shaft including a spring wound by movement of said manually settable control switch for returning said control switch to an initial position and driving said switching mechanism, said spring driven switching mechanism including a cam member having a number of individual cam surfaces and mounted to said shaft, and said switching means including a plurality of switches for individually controlling said motor, heater and blower and engaging individual ones of said cam surfaces.

3. Apparatus as in claim 2 wherein said means for locking includes a sprin biased armature, a rotatable locking plate, a sprocke rotatable with said shaft and in engagement with said plate, and an electromagnet for attracting said armature to lock said plate thereby preventing rotation of said sprocket to prevent rotation of said shaft and said manually settable control switch.

4. Apparatus as in claim 3 further comprising alarm means for indicating the locking of said shaft and manually settable control switch. 

1. Apparatus for controlling a drier, comprising: a heater, blower, and motor for providing rotative movement; a rotatable drier housing; means mounted within said housing for determining the water content of the material within said housing; switching means for controlling the operation of at least said motor, heater and blower; a manually settable control switch for setting the desired dryness of said material; a spring driven switching mechanism actuated by settable control switch for controlling said switching means; a control circuit for comparing the wetness of said material with said value of preset dryness; and means for locking said spring driven switching mechanism whereby said spring driven switching mechanism is unlocked with said control means indicating that said material has reached said desired degree of dryness, said means for locking is inoperative prior to actuation by said control means.
 2. Apparatus as in claim 1 further comprising a rotatable shaft interconnecting said manually settable control switch and said spring driven switching mechanism, said shaft including a spring wound by movement of said manually settable control switch for returning said control switch to an initial position and driving said switching mechanism, said spring driven switching mechanism including a cam member having a number of individual cam surfaces and mounted to said shaft, and said switching means including a plurality of switches for individually controlling said motor, heater and blower and engaging individual ones of said cam surfaces.
 3. Apparatus as in claim 2 wherein said means for locking includes a spring biased armature, a rotatable locking plate, a sprocket rotatable with said shaft and in engagement with said plate, and an electromagnet for attracting said armature to lock said plate thereby preventing rotation of said sprocket to prevent rotation of said shaft and said manually settable control switch.
 4. Apparatus as in claim 3 further comprising alarm means for indicating the locking of said shaft and manually settable control switch. 